Jacksonville actually owns one of the league's most underrated defenses, as the team currently ranks fifth in the NFL in yards allowed per game and 11th in points allowed per game. Jacksonville is no cake walk for any offense.

The Seahawks defense is another vastly underrated unit, as they currently rank sixth in the league in points allowed per game. Seattle's defense has made some of the game's elite offenses look sluggish.

The defense has finally begun playing elite football like it was expected to when the season began. The unit currently ranks fifth in the NFL in points allowed per game. The Dolphins have shut down some of the best offenses in football this year.

The Bengals have been a very solid defense this year, as they currently rank 10th in the league in points allowed per game and sixth in yards allowed per game. This young and growing unit will be one of the most intimidating in the league in a few seasons.

4. Houston Texans

The Houston Texans have been one of the most surprising defenses in the league this season.

After owning the distinction of being the NFL's worst passing defense last year, the Texans have really turned it around.

Defensive coordinator Wade Phillips has reinvigorated a once-depleted unit by bringing in young stars at important positions.

Newly acquired cornerback Jonathan Joseph has been one of the best defensive backs all season long, as he has drastically improved Houston's secondary.

The unit currently ranks second in the NFL in yards allowed per game, as well as fourth in points allowed per game.

The Texans' pass-rush, even without Mario Williams, has been one of the best in the league this season. The team currently ranks seventh in the NFL in sacks, largely due to the emergence of rookie defensive end JJ Watt and outside linebacker Connor Barwin as elite pass-rushers.

Houston's defensive turnaround has helped lead the franchise to it's first ever postseason appearance. The unit is a complete group, as they rank in the Top Five in numerous statistical categories.

Superstar linebacker Terrell Suggs leads one of the most feared pass-rushes in all of football.

Former Super Bowl MVP Ray Lewis is a jack of all trades, as he is superb in rushing the passer and dropping back in coverage, and ball-hog safety Ed Reed instills fear into any opposing quarterback.

These four players are all perhaps the best in the league at their respective positions. They help lead an amazing defense that currently ranks third in points allowed per game, third in yards allowed per game and first in sacks.

Without this colossal unit, the Ravens would be just an average team. The Baltimore defense is superb in all aspects of the game and is one of the most complete groups in the league today.

1. Pittsburgh Steelers

The Steelers' amazing defense currently ranks first in yards allowed per game and second in points allowed per game, even when facing explosive offenses week after week.

Pittsburgh boasts some of the most feared defenders in the NFL. These include superb pass-rushers James Harrison and Lamar Woodley, who have combined for 17 sacks.

Those two beasts, along with elite inside linebackers Lawrence Timmons and James Farrior, form one of the league's best linebacker corps.

The Steelers run defense ranks among the best in the game, as monstrous nose tackle Casey Hampton shuts down opposing running backs.

The Steel Curtain's secondary is also one of the best in the league.

Safety Troy Polamalu is one of the most feared defenders in the game today. He is a complete player, as his skills range from rushing the passer to covering some of the league's most dominant wide receivers.

The secondary also included safety Ryan Clark, who is responsible for some of the most bone-crushing hits in recent history, and underrated cornerback Ike Taylor.

Pittsburgh's defense is far and away the most feared unit in the league. Opposing offenses dread facing this completely unmerciful group, especially in Heinz Field.